Internal combustion percussion tools and hammer pistons for such tools



Oct. 2, 1962 B. v. NYHOLM 3,056,390

INTERNAL COMBUSTION PERCUSSION TOOLS AND HAMMER PISTONS FOR SUCH TOOLSFiled March 31, 1959 5 Sheets-Sheet l ATTORNEY Oct. 2, 1962 B. v. NYHOLM3,056,390

INTERNAL COMBUSTION PERCUSSION TOOLS AND HAMMER PISTONS FOR SUCH TOOLSFiled March 31, 1959 5 Sheets-Sheet 2 Fig.2

INVEN OR I WM A46 i ATTORNEY Oct. 2, 1962 B. v. NYHOLM INTERNALCOMBUSTION PERCUSSION TOOLS AND HAMMER PISTONS FOR SUCH TOOLS 5Sheets-Sheet 3 Filed March 31, 1959 Fig. 5

United States Patent C) INTERNAL COMBUSTIUN PERCUSSION TOOLS AND HAMMERPISTONS FOR SUCH TOOLS Bengt Viktor Nyholm, Nacka, Sweden, assignor toAtlas Copco Aktiebolag, Nacka, Sweden, a corporation of Sweden FiledMar. 31, 1959, Ser. No. 803,168 1 Claim. (Cl. 123-7) This inventionrelates to improvements in internal combustion percussion tools having areciprocabie tree piston actuated by combustion gases for producing thepercussion stroke and by pressure gas or air in a chamber in the toolfor producing the return stroke of the free piston. Such tools areprimarily used as concrete breakers and as rock drills for drillingholes of moderate depths as may be needed for erection of power lineposts, building foundations, sewage and water pipe trenches and thelike. For all these different jobs the low weight of the tool is ofoutstanding importance for the ease of handling it. Another veryimportant feature is to provide a tool which produces a heavy blowwithout injury to the hammer piston or the working implement. One objectof the invention is to provide a tool which incorporates a hammer pistonmaking possible the design of a tool in which the above features arecombined in a manner resulting in a dependable efficient tool of aweight about fifty five pounds or less and are capable of drilling holesfrom a few feet up to 1( 15 feet and to do the other work demanded fromthe tool.

In the accompanying drawings one embodiment of an internal combustionpercussion tool according to the invention is illustrated by Way ofexample it being understood, however, that various modifications of thein vention may be made within the scope of the claim. FIG. 1 is alongitudinal section of the tool on a plane including a crank shaftincorporated in the tool which has a combined motor and compressorpiston connected to the crank shaft and a free opposed motion piston.FIG. 2 is a longitudinal section of the tool on a plane perpendicular tothe crank shaft. FIG. 3 is a detail section of one end of the crankshaft and cooperating means for transmitting motion to a drill steelrotation mechanism. FIG. 4 illustrates on a larger scale a lower housingforming a part of the tool and containing means for engaging anddisengaging a drill steel rotation mechanism. FIG. 5 is a viewsubstantially on line V-V in FIG. 4, and FIGS. 6, 7 and 8 are crosssections on line VIVI in FIG. 5 showing a disengaging and valve memberin various positions. FIG. 9 is a longitudinal section of the freemoving piston of the tool.

The percussion tool illustrated on the drawings has a casing comprisinga crank case 1, 2, a compressor cylinder 3, a motor cylinder 4, anauxiliary cylinder 5, and a lower housing 6. The motor cylinder 4 andthe auxiliary cylinder 5 may preferably be made integral. A crank shaft7 is journalled for rotation in the crank case 1, 2, which has twohandles 8, 8 provided thereon. The crank case carries a fuel tank 9 andthe crank shaft carries a flywheel 10 provided with a rope starter drum11 for starting of the tool, a magneto 12 for generating ignitioncurrent, and a cooling fan 13 operating in a spiral housing 14 formed inthe crank case portion 2. A connecting rod 15 is journalled on the crankpin of ice the crank shaft 7 and connected by means of a piston pin 16to a combined motor and compressor piston. Said piston which is adifierential trunk piston consists of a motor portion 17, a sleeveportion 18, and a com pressor portion 19. The motor portion 17 inconventional manner controls openings in the cylinder 4 through whichscavenging air and fuel is supplied to the combustion chamber 29 in themotor cylinder through passages 20' leading to the combustion chamberfrom the crank case. Scavenging air is drawn into the crank case andcompressed therein by the combined motor and compressor piston 17, 19.Fuel is supplied to the scavenging air from the fuel tank 9 by means ofa carburetter (not illustrated) in conventional manner. 21 indicates aspark plug and 22 an exhaust manifold. 23 indicates sealing ringsprovided between the combustion and cornpressor cylinders and forming aseal with the sleeve portion 18 of the differential piston.

The compressor portion 19 draws air through an opening controlled by avalve 24- into an annular compressor cylinder chamber 25 and compressesthe air therein and delivers it over a valve 26 through a conduit 27 toa chamber 28 in the lower housing 6. A free piston, FIG. 9, formed as acombined motor, hammer, damper and return stroke producing piston isreciprocable in the combustion cylinder chamber 29, an auxiliarycylinder chamber 39 with larger diameter than said combustion cylinderchamber, and in a bore 31 in a guide member 32 having a diameter whichis half the diameter of the combustion cylinder bore or more. The freepiston consists of a motor portion 33 fitting in the combustion cylinderchamber 29 and provided with piston rings, a portion 34 with largerdiameter, movable in the auxiliary cylinder, and a blow deliveringhammer portion 35 with a smooth cylindrical surface extending oversubstantially the whole length of said hammer portion and sealing thebore 31 in the guide member 32. In order to give sufficient weight tothe free piston said piston is made solid and with the motor portion 33at least as long as the hammer portion 35 and the damper portion 34together. The smooth comparatively large hammer portion 35 is strongenough to Withstand the stresses produced by the blows for a long timeand still the whole free piston is sufiiciently elastic not to exposethe working implement to undesirable stresses. Finally the free pistonis so short that the whole tool length and the weight of the tool may bekept within permissible limits and in practice a tool weight of 50-55pounds is maintained according to the invention.

Air compressed by the compressor portion 19 in the chamber 25 flows fromthe chamber 28 through openings 36 into an annular space 37 on the upperside of the free piston portion 34 and through openings 38 into thechamber 39 in the auxiliary cylinder 5 defined by the lower face of thepiston portion 34 and the guide member 32 which forms the lower head orbottom of the chamber 39. Below the guide member 32 a chamber 40 isformed in the lower housing 6 which in the illustrated embodimentaccommodates drill steel turning mechanism. However, in tools not usedfor rock drilling said rotation mechanism may be dispensed with.

In the illustrated tool, a drill steel chuck 41 is rotatably journalledin the lower housing 6, which also carries a I drill steel retainer 42,swingably mounted on the lower housing 5 as is obvious from FIG. 2, andcapable of retaining a drill steel 43 or other working implement. Theupper end face of the drill steel chuck 41 together with the lower endface of the guide member 32 form a thrust bearing with large bearingsurfaces for transmitting the aXial thrust on the working implement fromthe tool casing, i.e. the feed pressure. The drill steel chuck may beprovided with interlocking means, such as a transverse pin inserted inthe lower casing and entering a corresponding hole in the chuck so thatturning of the chuck may be prevented when it is desired to use the toolas a concrete breaker, or as a spade tool, or the like.

The openings 36 and 38 serve to admit compressed air into the chambers37 and 39 as aforesaid. The air cushion in the chamber 37 prevents thefree piston from hitting the upper end wall of the annular chamber 37with the annular piston portion 34. A passage 44, leads from the chamber28 to the chamber 49, said passage be ing controlled by an adjustingscrew 46. From the chamber 40 passages 47 in the guide member 32 lead toa space surrounding the blow receiving end of the shank 48 of the drillsteel 43 which has a conventional flushing passage (not illustrated)normally opening in said space but for the short moments when the freepiston delivers the blows. A packing 49 prevents flushing air in thechamber 40 from leaking to the atmosphere between the shank 48 of thedrill steel and the drill chuck 41.

In order to make possible turning of the drill steel 43 the chuck 41forms a ratchet wheel 50 provided with teeth cooperating with a pawl 51operated to rotate the ratchet wheel 50 in a certain direction. For thispurpose the pawl 51 is hingedly connected to an arm 52 provided on ashaft 53 which oscillates during the operation of the tool. A spring 54,FIG. 5, normally keeps the pawl 51 in a position in which it engages theratchet wheel 50. The oscillating turning movement of the shaft 53 isderived from the crank shaft 7 which for this purpose has a pin 55 atone end set at an angle with respect to the longitudinal rotation axisof the shaft 7, as is obvious from FIGS. 1 and 3. A block 5'6 is mountedon said pin 55 and said block is slidable in the forked end 57 of theoscillatable shaft 53. When the crank shaft 7 turns one revolution thiswell known motion transmission causes the shaft 53 and arm 52 to producean oscillating turning movement which causes the pawl 51 to reciprocateand turn the ratchet wheel 50 and the drill steel chuck 41 therebyturning the drill steel.

A disengaging and valve member 58 is rotatably and axially displaceablymounted in the lower housing 6. The member 58 may be said to be acombined sleeve valve and disengaging means for the pawl 51. The member58 is provided with a handle 59 accessible from the outside of the lowerhousing 6 so that the member 58 may easily be turned. A spring loadedball lock 60 cooperates with a number of notches 61 in the member 58 toretain said member in various positions of adjustment. The member 58forms a seal in the lower housing 6 and is provided at its inner endwith an arm or finger 62 ending with a head 63 having a disc shape asindicated in chain dotted lines in FIGS. 6, 7 and 8 and arranged in sucha manner that the head in the position of the member 58 illustrated inFIGS. 4, 5 and 6 leaves the pawl 51 free to move for turning the ratchetwheel 50. The member 58 is provided with a cam groove 61 cooperatingwith a lug 65 formed on a screw 66 in such a manner that the member 58when turning by means of the handle 59 is displaced axially. Twopassages 67, 68 are provided in the lower housing 6 and lead, as isobvious from FIG. 4, from the chamber 39 to the atmosphere, saidpassages being controlled by the member 58. The member 58 has atransverse passage 69 and an axial peripheral goove 70 extending fromthe inner end of the sleeve portion of the member in the peripheralportion thereon.

The member 58 operates in the following manner. When the percussion toolis operated as a rock drill and is started the handle 59 is at firstturned from the position illustrated in FIGS. 4-6 causing the member 58to take the position illustrated in FIG. 7. During this turning motionthe member 53 is axially displaced so that the head 63 pulls the pawl 51out of engagement with the ratchet wheel 59. Consequently, no turning ofthe drill steel chuck can be produced when the crank shaft starts torotate. Simultaneously, the passage 69 connects the passages 67 and 68so that the chamber 39 is vented to the atmosphere. Consequently, thefree pis ton 33, 34, 35 remains in bottom end position. By means of astarter rope (not illustrated) the starter rope drum 11 is rotated andthe motor portion of the tool is started and the tool runs idle. Nopercussion work is then produced since the free piston 33, 34, 35 doesnever lift from its bottom position. As soon as the motor portion isrunning and the operator is ready to start drilling he places to toolwith the steel 43 against the spot to be drilled and turns the handle 5990 in reverse direction to the position illustrated in FIGS. 4, 5 and 6causing the venting passage from the chamber 39 to be closed and thepawl 51 to be moved into engagement with the ratchet wheel Si) by thespring 54. The weight of the tool causes the shank 48 of the steel 43 tolift the free piston 33, 34, 35 to the position in FIGS. 1 and 2. Thecompressed air produced by the compressor portion 19 in the chamber 25and supplied through the conduit 27 to the chamber 28 and admittedthrough the openings 33 to the chamber 39 lifts the free piston 33, 34,35 which starts to operate and to cooperate with the motor pistonportion 17. Compressed air simultaneously admitted through the openings36 to the annular chamber 37 provides an air cushion in said chamber.The tool now operates as a rock drill with air flushing of the drillhole.

If it is desired to use the tool as a concrete breaker or as a spadingtool or the like in which case rotation of the working implement is notdesired or permitted the drill steel 43 is replaced by a chisel or otherimplement which is inserted in the drill chuck 41. Starting of the toolis made after turning of the handle 59 so that the member 58 takes theposition illustrated in FIG. 7. The motor portion is then started in themanner above described and the too] runs idle. When the motor portionhas started the handle 5'9 is turned 90 to the position illustrated inFIG. 8. In this position the venting of the chamber 39 is interruptedbut the pawl 51 is still kept in inoperative position. Through thegroove 70 which is now connected with its inner end to the opening 68venting of the chamber 40 is obtained so that supply of flushing air isinterrupted. The shank of the implement lifts the free piston in thesame way as in drilling and the free piston 33, 34, 35 now operates andreciprocates and delivers impacts to the tool implement but withoutturning the implement, i.e. the tool operates as a concrete breaker, aspade tool, or the like.

The tool above described and illustrated in the drawings should beconsidered only as an example and the details of the tool may be variedin various diiferent ways within the scope of the claim. The inventionmay for instance be employed in combustion gas driven tools in which norotation mechanism for the implement is provided.

What I claim is:

An internal combusion percussion tool comprising in combination acasing, a combustion cylinder in said casing, a combustion cylinder insaid caisng, an auxiliary cylinder of larger diameter than saidcombustion cylinder in said casing, a guide member having a bore withless diameter than said combustion cylinder coaxial with said combustioncylinder, a free differential piston having a motor portion reciprocableand guided in said combustion cylinder and an integral cylinder hammerportion reciprocable and guided in said bore and having a cylindricalsealing surface extending along substantially the whole length of saidhammer portion and a damper and return stroke producing portionreciprocable in said auxiliary cylinder, the length of the motor portionof said difierential piston being at least as great as the combinedlengths of said hammer and damper portions, a tool chuck rotatable insaid casing, a motor piston reciprocable in the combustion cylinder inopposition to said free piston, a crank mechanism mounted for rotationin the casing and connected to said motor piston, positive aircompressing means having a greater displacement than the displacement ofsaid motor piston connected to said crank mechanism, means connectingsaid air compressing means to said auxiliary cylinder for delivering airunder pressure to said air auxiliary cylinder for producing said returnstroke and a chuck rotation mechanism capable of being coupled to saidchuck for rotation of the chuck and driven by said crank mechanism.

References (lited in the file of this patent UNITED STATES PATENTS1,920,765 Rasch Aug. 1, 1933 2,479,593 Weyandt Aug. 23, 1949 2,686,501McKelvy Aug. 17, 1954 2,764,138 Wahlsten et a1. Sept. 25, 1956 2,854,962Bergman Oct. 7, 1958 2,857,888 Guthrie Oct. 28, 1958

